Code Definition

B2511 — Horn Output Relay Circuit Short to Battery

System: Body  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About B2511

B2511 is a generic (obd-ii standard) body diagnostic trouble code. It belongs to the B-prefix family of codes, which covers body, interior, airbag, or comfort-electronics faults.

When B2511 is stored, the module has detected a short-circuit (voltage pulled to ground or to supply) in the monitored circuit.

Scanning & clearing: Body (B) codes are often stored in the body control module, airbag module, or climate module. A basic OBD-II tool usually will not read body codes — an enhanced or OEM-level scan tool is typically required.

Because B2511 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The Body Control Module (BCM) monitors the horn output relay control circuit using a sense line on its low side driver output. DTC B2511 is set when the BCM detects battery voltage on the horn relay control line when it should be off, indicating an unintended short to battery on that wire. Because the horn relay is typically switched on the ground side by the BCM, a short to battery on the control wire keeps the relay energised and the horn sounding regardless of horn switch input. When this code sets the horn may sound continuously or intermittently, the BCM may disable the horn driver to pro...

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